Recent research suggests that intermittent fasting may not offer a significant advantage for weight loss compared to less structured approaches, including doing nothing at all. This finding comes from a comprehensive review of studies involving individuals classified as overweight or obese.
Intermittent fasting has gained considerable traction as a popular strategy for shedding pounds. This dietary approach involves cycles of abstaining from food and consuming it. Common methods include daily time-restricted eating, such as the 16:8 diet where eating is confined to an 8-hour window and fasting lasts for 16 hours. Alternatively, some follow a pattern like the 5:2 diet, restricting calories significantly on two days of the week while eating normally on the other five.
The underlying principle suggests that by limiting the time available for eating, individuals naturally reduce their overall calorie intake. However, one randomized-controlled trial indicated that this method is no more effective for weight loss than simply counting calories.
To investigate further, Luis Garegnani from the Italian Hospital of Buenos Aires in Argentina, along with his colleagues, examined data from 22 randomized-controlled trials. These studies encompassed nearly 2,000 adults residing in North America, Europe, China, Australia, and South America. The participants’ ages ranged from 18 to 80, and all were either overweight or had obesity.
Their initial comparison involved intermittent fasting against standard dietary advice. The researchers concluded that there was likely no substantial difference in weight loss outcomes between the two. Further, when comparing intermittent fasting to a control group that engaged in no specific weight loss intervention, the results indicated that such fasting likely does not lead to greater weight loss. Garegnani stated in a press release, “Intermittent fasting just doesn’t seem to work for overweight or obese adults trying to lose weight.”
Despite these findings, Garegnani acknowledges that inconsistencies across the reviewed trials present challenges in forming definitive conclusions. Nevertheless, even when the results were segmented by gender or the specific type of intermittent fasting employed, the approach still did not appear to contribute to more effective weight loss.
Satchidananda Panda of the Salk Institute for Biological Studies in California raised a critical point regarding the review’s methodology. He noted that the majority of studies included did not rigorously measure participants’ adherence to the intermittent fasting protocols. “If we don’t know whether participants actually followed the intervention, what, exactly, are we systematically reviewing?” he questioned. He likened the situation to “building a cathedral on quicksand and then performing a meta-analysis of the architecture.”
The analysis concentrated solely on weight loss. Consequently, the review does not offer clarity on whether intermittent fasting has other health impacts, positive or negative. For instance, some research hints that it might elevate the risk of heart disease, while other studies suggest it could bolster immunity and enhance gut and liver function.
“Intermittent fasting is not a miracle solution,” Garegnani added. “[It] may be a useful option for some individuals, but it shouldn’t distract from broader, population-level strategies to prevent and manage obesity.”
Journal reference: Cochrane Database of Systematic Reviews DOI: 10.1002/14651858.CD015610.pub2